Apparatus for heating and spraying lacquer or the like



Aug. 1, A, L STEVENS APPARATUS FOR HEATING AND SPRAYING LACQUER OR THELIKE Filed March 10, 1948 i A A 1/0 you; 54 LAMP 35 I INVENTOR r/4rt/zur1.. 5561/6/75 a W M! ATTORNEYJ forgetting the apparatus into optimumPatented Aug. 1, 1950 APPARATUS FOR HEATING AND SPRAYING LACQUER OR THEArthur L. Stevens, Buffalo, N. Y.

Application March 10, 1948, Serial No. 14,116

8 Claims.

This invention relates to apparatus for heating and spraying coatingmaterials such as lacquer, varnish, aircraft dopes, paints, or otherchemical compositions wherever it is advantageous to spray the coatingmaterials while in heated condition. For example, it is known thatnitrocellulose type lacquers may be more efllciently and perfectlyapplied in furniture finishing operations and the like if the lacquer isheated before it goes to the spray gun, and that such heatingtemporarily lowers the viscosity of the material and thereby reduces thechemical thinner content requirement with a resulting saving in cost.However, in the handling of lacquers or like compositions comprisingvolatile solvents and thinners, it is of prime importance to avoidheating of the lacquer supply except as it is about to be sprayed, andto avoid dangerous overheating and/or pressurizing of the lacquerhandling apparatus. It is also of prime importance in such work to avoidunnecessary heating of the entire lacquer supply prior to its beingdrawn into the active spray supply portion of the system; and in anycase to arrange to heat only a small quantity of lacquer at a time, sothat the required starting-up? period is minimized.

Therefore, it is an object of the present invention to provide animproved apparatus for drawing upon a supply of cold lacquer or the likefor the purpose of heating the lacquer and delivering it to a spray gun;the apparatus including improved temperature and pressure regulatingmeans and lacquer over-supply return means from the gun arranged so asto prevent return of hot lacquer to the cold lacquer supply tank.

Another object of the invention is to provide an improved heating andpressuring apparatus 2 temperature, irrespective of the rate of use ofthe material.

Another object of the invention is to provide an apparatus wherein thefeatures and advantages aforesaid are attained in an inexpensivelyfabricated unit of compact and readily portable form.

Another object of the invention is to provide an apparatus as aforesaidcomprising a novel combination of structurally simple and ruggedoperative and control elements.

Other objects and advantages of the invention will appear from thespecification hereinafter.

In the drawing:

Fig. 1 is a diagrammatic illustration of the mechanical features of anapparatus of the invention; and

Fig. 2 is a diagram of the electrical mechanism thereof.

The invention is illustrated in the drawing as being employed for thepurpose of drawing a supply of lacquer or the like from a tank or drumI0, and heating and feeding the lacquer to a spray gun as indicated atI2. The apparatus of the invention includes a positive displacement typefluid pump which is indicated at I4, and which is arranged to be drivenby a compressed air motor I5. The intake port of the pump I4 is coupledto a conduit Iii-which leads to the lacquer supply tank III, and a checkvalve I8 is preferably disposed in the line of the con-.

The discharge port of the pump II is connected to a conduit I9 which iscoiled as indicated at 20 and thence leads into communication with theinlet port of the spray gun as indicated at 22. A thermostat switch asindicated at 24 is disposed of the type aforesaid, which ischaracterized by brought rapidly up from cold condition to the desiredtemperature for spraying; thereby greatly reducing the starting.-up-timerequired sprayingcondition- Another object of the invention isto providean improved coating material heating and sprayin apparatus whereintheheated material is furnished to the spray headportion of the apparatusat substantiallyficonstant pressure and in the line of the conduit20-22, for purposes which will be explained hereinafter.

The fluid over-supply return port of the spray gun I2 is indicatedat 26,and is connected through a conduit 28 to the high pressure inlet of arelief valve 30. The valve 39 is of the,diaphragm type includingmanually adjustable spring means biasing the diaphragm, and the lowpressure port of thevalve 39 connects to a returnfcon'duit 32 I whichleadslback into the pumpintak'e conduit atfa position between the pumpand the check valve I8. Apr'essure'responsive electrical switch 34 isarranged with its pressure inlet turnconduit 32.

conduit "coupled into the "re- Thecoiled portion 2 of the rn Y i vheiconduitis nested within" a tank 35 con taining water and a heatingelement which is shown to be in the form of an immersion electricalresistance heater element designated 38 is also disposed within the tankto heat the water therein.

As shown in Fig. 2, the thermostat switch 24 and the pressure switch 34are connected in series with the heater element 38 by means ofconductors 40--4I which in turn connect into any suitable power supplysource, and a signal lamp is shunted across the conductors to indicatewhether or not the heater is energized. The entire mechanical andelectrical organization of the apparatus of the invention is preferablymounted upon a single baseboard, with the pump and coil and conduitparts relatively arranged as compactly as possible so that the entirefluid circulating system defined by the conduits i9- 2ll28,32 is ofminimized volumetric capacity. Thus, preparatory to a spraying operationa spray gun will be attached to the conduit connections 22-26 and a drumof lacquer or the like will be set in position relative to the intakeconduit l6, as illustrated in Fig. l of the drawing. The control devicegoverning operation of the motor 15 will then be set to cause the motorto operate, thereby drawing cold lacquer from the drama l through thecheck valve and thence into the coil 20 and filling the conduit systemi9--20--28-32 with lacquer; the closed spray gun valve being operable atthis time to shunt the lacquer from the conduit head 22 to the conduithead 26.

The machine attendant will simultaneously operate a switch or the liketo close the conductors 40--4l with their power source, and inasmuch asthe lacquer in the region of the thermostat switch 24 is cold thisswitch will be closed. As soon as the pressure within the circulatingconduit system equals the setting of the pressure responsive switch 34,the latter will be pressureoperated to complete the closing of theelectrical circuit to the heater 38 and the signal lamp. Thus, therelatively small quantity of lacquer within the closed conduit systemwill be thereby circulated over and over again and through the coil 20,whereby heat from the element 38 will be transferred through the tank ofwater and into the circulating lacquer as it moves through the coil.Consequently, in a relatively short time the lacquer within the closedcirculating system will be brought up to the desired sprayingtemperature, whereupon the operator may commence the spraying operationafter only a minimum "starting-up" loss of time.

Whenever the spray gun is operated the heated lacquer passes directlyfrom the conduit coil 20 through the gun and onto the work, and wheneverthe gun trigger pressure is relaxed the heated lacquer is shunted intothe return conduit 28. The valve 30 operates to maintain the pressure atthe spray gun approximately constant for optimum performance of the gun,but inasmuch as the demand for lacquer rate of discharge from the gunfluctuates widely in accord with the spraying operation requirements,the output load on the pump l4 will similarly vary. .Since the pump I4is preferably of the positive displacement type, for efiicient operationunder high pressure conditions, it is therefore preferred to employ acompressed air type motor as indicated at I for driving the pump. Bysupplying air to the motor l5 at constant pressure, the motorpump unitwill operate at correspondingly varying speeds so as to deliver therequired fluctuating volumes of lacquer under a constant pressure. Thevalve 30 alone would be incapable of furnishing the requiredvolume-to-pressure control under such widely fluctuating output demandconditions, and thus it is the combination and whenever the pump I4 isstopped, or in event of a mechanical failure resulting in loss ofoperating pressure within the conduit system, the pressure responsiveswitch 34 will operate automatically to de-energize the heater. A small"pin hole is preferably drilled through the disc of the check valve l8as indicated at 45, so as to permit a gradual bleeding oif of theoperative pressure within the conduit system whenever the apparatus isshut down. This insures opening of the pressure switch 34 andde-energization of the heating element when the apparatus is inactive,and therefore eliminates the possibility of accidental and dangerousoverheating incidental to shut downs. Also, the opening through thecheck valve operates at all times in the manner of a safety outlet,permitting escape of excessive pressures from the system.

Thus, it will be appreciated that the apparatus of the inventioncomprises a mechanically and electrically simple operative and controlorganization which maintains the spraying lacquer at constanttemperature and pressure;- and which is characterized particularly inthat only a small quantity of lacquer is required to fill thestarting-up circulating and heating system of the apparatus, whereby itmay be brought into full operation within a minimum of time after acold" start. It will also be appreciated that by reason of thearrangement of the over supply return conduit system, return of "hotlacquer to the cold" lacquer supply tank is avoided. This avoids heatingof large quantities of lacquers and minimizes evaporation losses of thevolatile solvents in the material being handled.

It will also be appreciated that although one specific form of theapparatus of the invention has been shown and described in detailherein, it will be apparent to those skilled in the art that theinvention is not so limited but that various changes may be made thereinwithout departing from the spirit of the invention or the scope of theappended claims.

I claim:

1. In a liquid heating and spray system, in combination, a spray gun, aliquid supply source under atmospheric pressure, a continuously operatedpositive displacement pump, liquid intake conduit means connecting saidsource to the intake of said pump, a discharge conduit connected to thedischarge port of said pump and to the intake connection of said spraygun, a heater arranged in heat exchange relation with said dischargeconduit, a return conduit connected to the return connection of saidspray gun and to the intake port of said pump, a pressure regulator insaid return conduit to maintain a constant pressure at said spray gun,means responsive to the temperature of the fluid within said dischargeconduit for regulating operation of said heater, and a check valve insaid intake conduit.

2. In a liquid heating and spray system, in combination, a spray gun, aliquid supply source under atmospheric pressure, a continuously operatedpositive displacement pump, liquid intake conduit means connecting saidsource to the intake of said pump, a discharge conduit connected to thedischarge port of said pump and to the intake connection of said spraygun and passin through a water bath, an electric heater rranged in heatexchange relation with said water bath, a return conduit connected tothe return connection of said spray gun and to the intake port of saidpump, a pressure regulator in said return conduit to maintain a constantpressure at said spray gun, thermostat means responsive to thetemperature of the fluid within said discharge conduit for regulatingoperation of said heater. and a check valve in said intake con-,

duit.

3. In a liquid heating and spray system, a spray gun, a continuouslyoperated pump, a discharge conduit connected to the discharge port ofsaid pump and to the intake connection or said spray gun, a heaterarranged in heat exchange relation with said discharge conduit, a returnconduit connected to the return connection of said spray gun and to theintake port of said pump, a pressure regulator in said return conduit tomaintain a constant pressure at said spray gun, means responsive to thetemperature of the fluid within said discharge conduit for regulatingoperation of said heater, means responsive to loss of pressure in saidreturn conduit to de-energize said heater, and a fresh fluid supplyconduit having a check valve therein and connected into the intake portof said pump.

4. In a liquid heating and spray system, a spray gun,acontinuouslyoperated positive displacement pump. a compressed air operated motordrivin said pump, a discharge conduit connected to the discharge port ofsaid pump and to the intake connection of said spray gun, a heaterarranged in heat exchange relation with said discharge conduit, a returnconduit connected to the return connection or said spray gun and to theintake port of said pump, a pressure regulator in said return conduit tomaintain a, constant pressure at said spray gun, means responsive to thetemperature of the fluid within said discharge conduit for regulatingoperation of said heater, means responsive to loss of pressure in saidreturn conduit to de-energize said heater, and a fresh fluid supplyconduit having a check valve therein and connected into the intake portof said pump.

5. In a liquid heating and spray system, in combination, a spray gun, aliquid supply source under atmospheric pressure, a continuously operatedpositive displacement pump, liquid intake conduit means connecting saidsource to the intake of said pump, a discharge conduit connected to thedischarge port oi said pump and to the intake connection of said spraygun and passing through a water bath, a heater arranged in heat exchangerelation with said water bath, a return conduit connected to the returnconnection of said spray gun and to the intake port of said pump, apressure regulator in said return conduit to maintain a constantpressure at said spray gun, means responsive to the temperature of thefluid within said discharge conduit tor regulating opcheck valve in saidcharge port of said pump and to the intake connection of said spray gunand passing through a water bath, a, heater arranged in heat exchangerelation with said water bath, a return conduit connected to the returnconnection of said spray gun and to the intake port of said pump, apressure regulator in said return conduit to maintain a constantpressure at said spray gun, thermostat means responsive to thetemperature of the fluid within said discharge conduit for regulatingoperation of said heater, means responsive to loss of pressure in saidreturn conduit to deenergize said heater, and a fresh fluid supplyconduit leading to the intake port of said pump.

7. In a liquid heating and spray system, a spray gun, a continuouslyoperated pump, a discharge conduit connected to the discharge port ofsaid pump and to the intake connection of said spray gun, a, heaterarranged in heat exchange relation with said discharge conduit, a returnconduit connected to the refurn connection of said spray gun and to theintake port of said pump, a pressure regulator in said return conduit tomaintain a constant pressure at said spray gun, means responsive to thetemperature of the fluid within said discharge conduit for regulatingoperation of said heater, means responsive to loss of pressure in saidreturn conduit to de-energize said heater, 8. fresh fluid supply conduitconnected into the intake port of said pump. and a check valve having asmall bleed of! opening therethrough in the line of said fresh fluidsupply conduit.

8. In a liquid heating and spray system, a spray gun, a continuouslyoperated positive displacement pump, a compressed air operated motordriving said pump, a discharge conduit connected to the discharge portof said pump-and to the intake connection of said spray gun, a heaterarranged in heat exchange relation with said discharge conduit, a returnconduit connected to the return connection of said spray gun and to theintake port of said pump, a pressure regulator in said return conduit tomaintain a constant pressure at said spray gun, means responsive to thetemperature or the fluid within said discharge conduit for regulatingoperation of said heater, means responsive to loss of pressure in saidreturn conduit to de-energize saidheater, a fresh fluid supply conduitconnected into the intake port of said pump, and an only partiallyclosing check valve in said fresh fluid supply conduit.

ARTHUR L. STEVENS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,266,354 Christenson et a]. Dec.16, 1941 2,366,150 Yount Dec. 26, 1944 2,378,184 Carlson June 12, 1945

